Delayed onset of vocal recognition in Australian sea lion pups (Neophoca cinerea)

In pinnipeds, maternal care strategies and colony density may influence a species' individual recognition system. We examined the onset of vocal recognition of mothers by Australian sea lion pups (Neophoca cinerea). At 2 months of age, pups responded significantly more to the calls of their own mothers than alien female calls demonstrating a finely tuned recognition system. However, newborn pups did not respond differentially to the calls of their mother from alien female calls suggesting that vocal recognition had not yet developed or is not yet expressed. These findings are in stark contrast to other otariid species where pups learn their mother's voice before their first separation. Variance in colony density, pup movements, and natal site fidelity may have reduced selective pressures on call recognition in young sea lions, or alternatively, another sensory system may be used for recognition in the early stage of life.9 page(s

Morphological and population genomic evidence that human faces have evolved to signal individual identity

Facial recognition plays a key role in human interactions, and there has been great interest in understanding the evolution of human abilities for individual recognition and tracking social relationships. Individual recognition requires sufficient cognitive abilities and phenotypic diversity within a population for discrimination to be possible. Despite the importance of facial recognition in humans, the evolution of facial identity has received little attention. Here we demonstrate that faces evolved to signal individual identity under negative frequency-dependent selection. Faces show elevated phenotypic variation and lower between-trait correlations compared to other traits. Regions surrounding face-associated SNPs show elevated diversity consistent with frequency-dependent selection. Genetic variation maintained by identity signaling tends to be shared across populations and, for some loci, predates the origin of Homo sapiens. Studies of human social evolution tend to emphasize cognitive adaptations but we show that social evolution has shaped patterns of human phenotypic and genetic diversity as well